U.S. patent number 7,505,504 [Application Number 11/576,792] was granted by the patent office on 2009-03-17 for laser processing device.
This patent grant is currently assigned to Sango Co., Ltd.. Invention is credited to Hidenori Nakano, Hirotaka Sakai, Tetsuya Watabe.
United States Patent |
7,505,504 |
Sakai , et al. |
March 17, 2009 |
Laser processing device
Abstract
A laser processing device in which even a short nozzle provided
with a follower roller (35) can prevent disturbance of a laser beam
and contamination of protective glass and in which shield gas can
act effectively. The laser processing device comprises a head
section (11) from which a laser beam that is condensed by a
condenser lens (16) provided inside the device is irradiated
through a nozzle section (13); a gas delivery means (28) opened in
a processing direction X, in the vicinity of the focal point of
laser beam, and jetting a shield gas from the opening; a primary
air delivery means (31) directed in the processing direction X,
above the focal point F of the laser beam, and jetting primary air
A1 substantially in the horizontal direction to form a first air
curtain; and secondary air delivery means (18, 13, 19) directed to
the focal point from the vicinity of the condenser lens and jetting
secondary air A2 to form a second air curtain.
Inventors: |
Sakai; Hirotaka (Miyoshi,
JP), Watabe; Tetsuya (Miyoshi, JP), Nakano;
Hidenori (Miyoshi, JP) |
Assignee: |
Sango Co., Ltd. (Aichi,
JP)
|
Family
ID: |
36142748 |
Appl.
No.: |
11/576,792 |
Filed: |
October 6, 2005 |
PCT
Filed: |
October 06, 2005 |
PCT No.: |
PCT/JP2005/018563 |
371(c)(1),(2),(4) Date: |
April 05, 2007 |
PCT
Pub. No.: |
WO2006/038678 |
PCT
Pub. Date: |
April 13, 2006 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20080031298 A1 |
Feb 7, 2008 |
|
Foreign Application Priority Data
|
|
|
|
|
Oct 7, 2004 [JP] |
|
|
2004-294938 |
|
Current U.S.
Class: |
372/55; 372/56;
372/60 |
Current CPC
Class: |
B23K
26/0648 (20130101); B23K 26/0665 (20130101); B23K
26/0823 (20130101); B23K 26/10 (20130101); B23K
26/123 (20130101); B23K 26/147 (20130101); B23K
26/38 (20130101); B23K 26/142 (20151001); B23K
26/064 (20151001); B23K 26/037 (20151001); B23K
26/24 (20130101); B23K 26/28 (20130101) |
Current International
Class: |
H01S
3/22 (20060101) |
Field of
Search: |
;372/55,59,60 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
63-264291 |
|
Nov 1988 |
|
JP |
|
1989114189 |
|
Aug 1989 |
|
JP |
|
3110094 |
|
May 1991 |
|
JP |
|
06079489 |
|
Mar 1994 |
|
JP |
|
06122089 |
|
May 1994 |
|
JP |
|
7503904 |
|
Apr 1995 |
|
JP |
|
2514138 |
|
Apr 1996 |
|
JP |
|
11788 |
|
Jan 1999 |
|
JP |
|
1158048 |
|
Mar 1999 |
|
JP |
|
11216589 |
|
Aug 1999 |
|
JP |
|
11-216589 |
|
Oct 1999 |
|
JP |
|
2000263276 |
|
Sep 2000 |
|
JP |
|
3312896 |
|
May 2002 |
|
JP |
|
3482452 |
|
Oct 2003 |
|
JP |
|
93 016838 |
|
Sep 1993 |
|
WO |
|
Other References
PCT International Search Report dated Dec. 13, 2005. cited by
other.
|
Primary Examiner: Nguyen; Dung T
Attorney, Agent or Firm: Dickinson Wright, PLLC
Claims
The invention claimed is:
1. A laser processing device comprising: a head section wherein a
laser beam condensed by a built-in condenser lens is radiated
through a nozzle section provided on a lower part of said head
section; a shield gas delivery section which is disposed below said
nozzle section and opens oriented in the progressing direction of
processing in the vicinity of the focal point of the laser beam and
jets out shield gas from the opening; a primary air delivery
section which is disposed apart from said head section and is
oriented in the progressing direction of processing above said
shield gas delivery section and forms a first air curtain by
jetting out primary air in a substantially horizontal direction;
and a secondary air delivery section which is oriented in the
focusing direction from the vicinity of said condenser lens and
forms a second air curtain by jetting out secondary air.
2. The laser processing device as claimed in claim 1, wherein said
primary air delivery section has slit-shaped outlets and a covering
member which surrounds the primary air flow and permits the passage
of a laser beam, and said secondary air delivery section is so
configured as to jet out secondary air from around said condenser
lens into the nozzle.
3. The laser processing device as claimed in claim 1, wherein the
flow rate of said primary air is set greater than the flow rate of
said secondary air when processing is to take place.
4. The laser processing device as claimed in claim 2, wherein the
flow rate of said primary air is set greater than the flow rate of
said secondary air when processing is to take place.
5. The laser processing device as claimed in claim 1, wherein a
following roller rotatably pivots on a supporting arm extending
from said head section, and the head section is displaced following
the following roller.
6. The laser processing device as claimed in claim 2, wherein a
following roller rotatably pivots on a supporting arm extending
from said head section, and the head section is displaced following
the following roller.
7. The laser processing device as claimed in claim 3, wherein a
following roller rotatably pivots on a supporting arm extending
from said head section, and the head section is displaced following
the following roller.
8. The laser processing device as claimed in claim 4, wherein a
following roller rotatably pivots on a supporting arm extending
from said head section, and the head section is displaced following
the following roller.
9. The laser processing device as claimed in claim 5, wherein wiper
members are further provided to reject sticking matter on side
faces of said following roller.
10. The laser processing device as claimed in claim 6, wherein
wiper members are further provided to reject sticking matter on
side faces of said following roller.
11. The laser processing device as claimed in claim 7, wherein
wiper members are further provided to reject sticking matter on
side faces of said following roller.
12. The laser processing device as claimed in claim 8, wherein
wiper members are further provided to reject sticking matter on
side faces of said following roller.
Description
TECHNICAL FIELD
The present invention relates to a laser processing device.
BACKGROUND ART
In a conventional laser welding practice, a tapered nozzle
(hereinafter referred to as a long nozzle) covers a region from the
lenses to the close vicinity of the focal point, to protect the
laser beam from a disturbance such as smoke (fume or plasma plume),
sputters (scattered molten powder) or the like (hereinafter
referred to as floating matters) until the laser beam reaches the
focal point (the weld of the work) or to prevent floating matters
from sticking to the condenser lens in the upper part or the
protective glass underneath it. It is also known that shield gas,
indispensable for welding, is jetted from a guiding channel
disposed in the long nozzle in combination with it (see Patent
Document 1).
Furthermore, while it is necessary in laser welding to position the
focal point of the laser beam on the surface of the work (or
somewhat within the work) with high precision, it is difficult to
keep the focal distance constant while moving the beam in the
welding direction, especially so where the weld is not flat. To
address this problem, it is also known to provide a roller in a
position orthogonal to the proceeding direction of welding relative
to the focal part of the laser beam and forcibly keep the focal
distance with the roller following along the surface of the work
(see Patent Documents 1, 2 and 3).
Also, it is an extensively adopted practice to arrange the guiding
channel and jetting outlet (hereinafter referred to as a side
nozzle) of shield gas so as to extend very closer to the focal
point independently of the main nozzle with the aim of preventing
shield gas from flowing in too large a volume and from
diffusing.
Since this method inevitably entails an arrangement in which the
length of the main nozzle is kept short to avoid interference with
the side nozzle and the side nozzle is positioned between the focal
point and the short main nozzle, the shielding effect of the long
nozzle against floating matters cannot be expected, making the
disturbance of the laser beam and the contamination of the
protective glass unavoidable.
Known techniques to address this problem include providing another
air jetting outlet between the short nozzle and the shield gas
jetting outlet and jetting out a substantially horizontal air
curtain from there to prevent floating matters from shifting upward
(being blown up) (see Patent Documents 4 and 5).
Still other known techniques include the addition of a large duct,
slit passage of air (lamination of the air flow) and focusing of
inert gas to the focal point (downward orientation) for
strengthening the air curtain effect (see Patent Document 6).
Patent Document 1: JP-A-3-110094
Patent Document 2: JP-B2-3312896
Patent Document 3: JP-B2-3482452
Patent Document 4: JP-A-6-122089
Patent Document 5: JP-A-2000-263276
Patent Document 6: JP-A-6-79489
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
If the following roller disclosed in Patent Document 2 or 3 is
installed beside the long nozzle in a direction orthogonal to the
proceeding direction of welding described in Patent Document 1
cited above, there will arise a problem that the desire to bring
the contact between the roller and the work as close as possible to
the focal point poses an obstacle to increasing the nozzle
diameter.
Furthermore, since high power laser welding has come to be required
nowadays, and this requirement necessitates increasing the lens
diameter and reducing the focal distance, the long nozzle
inevitably has to be made larger in overall size and in diameter.
Therefore, it is difficult to combine Patent Documents 1 and 2 or 3
and equip the long nozzle with the roller. Moreover, the additional
installation of the shield gas guiding channel within the long
nozzle makes it even more difficult.
A shield gas guiding channel additionally installed in the long
nozzle is inherently susceptible to insufficiency in flow rate, but
expanding the sectional area of the guiding path would entail an
increase in long nozzle size, and this as well as the above is
incompatible with the pursuit of greater output.
However, if the space for the roller is secured by removing part of
the long nozzle unit to make it a short nozzle, it will become
impossible to avoid the problems of the disturbance to the laser
beam and the contamination of the protective glass. There has been
a call for a laser welding apparatus which, even if its short
nozzle is equipped with a following roller, is free from the
disturbance to the laser beam and the contamination of the
protective glass.
Or, in a configuration in which another air jetting outlet is
disposed between the short nozzle and the shield gas jetting outlet
and an air curtain is jetted out from it substantially
horizontally, as described in Patent Document 4 or 5 cited above,
though it is effective in preventing floating matters in the air
curtain area from being blown up, the configuration not only is
unable to prevent floating matters outside the area from being
blown up, but also positively causes part of the floating matters
to shift upward by rolling in the air flow, resulting in failure to
solve the problems of the disturbance to the laser beam and the
contamination of the protective glass.
Patent Document 6 cited above also leaves the problem of rolling-in
unsolved, failing to completely obstruct floating matters from
shifting upward. Besides that, the downward jetting of a powerful
air curtain gives rise to a new problem of rolling in even the
all-important shield gas and diffusing it.
On account of these circumstances, there is a keen call for a laser
processing apparatus which, even if it is equipped with the
following roller and has a short nozzle, can securely prevent the
disturbance to the laser beam and the contamination of the
protective glass and enables shield gas to function
effectively.
Now, an object of the present invention is to provide a laser
processing device which can meet this call.
BRIEF SUMMARY OF THE INVENTION
Means for Solving the Problem
In order to achieve the object stated above, according to a first
aspect of the invention, a laser processing device is characterized
in that there are provided a head section wherein a laser beam
condensed by a built-in condenser lens is radiated through a nozzle
section; gas delivery means which opens oriented in the progressing
direction of processing in the vicinity of the focal point of the
laser beam and jets out shield gas from the opening; primary air
delivery means which is oriented in the progressing direction of
processing above the focal point of the laser beam and forms a
first air curtain by jetting out primary air in a substantially
horizontal direction; and secondary air delivery means which is
oriented in the focusing direction from the vicinity of the
condenser lens and forms a second air curtain by jetting out
secondary air.
According to a second aspect of the invention, in the first aspect
of the invention, the primary air delivery means has slit-shaped
outlets and a covering member which surrounds the primary air flow
and permits the passage of a laser beam, and the secondary air
delivery means is so configured as to jet out the secondary air
from around the condenser lens into the nozzle.
According to a third aspect of the invention, in the first or
second aspect of the invention, the flow rate of the primary air is
set greater than the flow rate of the secondary air when processing
is to take place.
According to a fourth aspect of the invention, in the first, second
or third aspect of the invention, a following roller rotatably
pivots on a supporting arm extending from the head section, and the
head section is displaced following the following roller.
According to a fifth aspect of the invention, in the fourth aspect
of the invention, wiper members are further provided to reject
sticking matters on side faces of the following roller.
EFFECTS OF THE INVENTION
According to the first aspect, floating matters blown up from the
laser processing section are rejected in the progressing direction
of processing with the flow of the primary air curtain formed of
the primary air, and the floating matters can be further prevented
from being blown up toward the condenser lens by the flow of the
secondary air curtain formed of the secondary air. Moreover, the
mutually reinforcing effect of the primary air curtain of the
primary air and the secondary air curtain of the secondary air
strengthens the rejection of the floating matters in the
progressing direction of processing.
Therefore, it is possible to provide a laser processing device
which, in spite of its short nozzle, can firmly prevent external
disturbance of the laser beam and contamination of the protective
glass and enables shield gas to function effectively.
According to the second aspect, since the primary air flows within
the cover member, the primary air curtain of that primary air is
formed satisfactorily, the rejection of the floating matters is
accomplished satisfactorily, and the secondary air curtain of the
secondary air is so formed as to surround the outer periphery of
the laser beam, whereby preventing the floating matters from
invading into the laser beam area. Therefore, the external
disturbance of the laser beam and the contamination of the
protective glass can be prevented even more effectively.
According to the third aspect, it is possible to further enhance
the mutually reinforcing effect of the primary air and the
secondary air by setting the flow rate of the primary air greater
than the flow rate of the secondary air.
As the fourth aspect, in the case of providing the following
roller, it is possible to provide a laser processing device which
can achieve the effect of keeping the focal point of the laser beam
matched with the processing position by that following roller and
is free from external disturbance of the laser beam and
contamination of the protective glass in spite of its short
nozzle.
According to the fifth aspect, it is possible to further prevent
sputters or the like from sticking to the following roller.
BEST MODE FOR CARRYING OUT THE INVENTION
One of the best modes for carrying out the present invention will
be described in detail below with reference to drawings.
FIG. 1 shows an overall view of a laser processing device according
to the invention as seen in the progressing direction of
processing; FIG. 2, the right side view of the device in FIG. 1;
FIG. 3, a plan view of the device in FIG. 1 as seen from above;
FIG. 4, a partially exploded side view as seen from the other side
of FIG. 2; FIG. 5, a view as seen in the progressing direction of
processing in FIG. 4; FIG. 6, a view showing the flows of primary
air and secondary air in a further exploded illustration of the
essential part in FIG. 4; FIG. 7, a view showing an example of
application of the laser processing device according to the
invention; and FIG. 8 illustrates the positioning of the direction
of indexing the work in FIG. 7.
The laser processing device according to the invention, intended
for use in welding a work by laser processing, cutting a work,
marking a work or the like, will be described with reference to an
embodiment of the invention in which the laser processing device is
applied to a welding apparatus. However, this is not meant to limit
the invention to these embodiments.
The fitting frame 1 of the present device is provided on the
processing machine body, not shown in FIG. 1, to be movable in the
vertical direction. The fitting frame 1 is moved up and down by an
actuator 70 disposed on a device body 71 as shown in FIG. 7.
The fitting frame 1 is provided with a shaft 2 in the vertical
direction as shown in FIG. 1, and the shaft 2 is provided with a
supporting member 3 to be movable in the up and down directions.
Further, an elastic member 4 consisting of a coil spring intervenes
concentrically with the shaft 2 between the upper end face of the
supporting member 3 and the upper side part of the frame 1 to give
constant downward pressure to the supporting member 3, and the
supporting member 3 is enabled to move upward relative to the
fitting frame 1 against the pressure of the elastic member 4.
Therefore, the supporting member 3 is floatingly supported to be
movable in the up and down directions.
A first supporting frame 5 is vertically fastened to the supporting
member 3, and a second supporting frame 6 is vertically fastened to
the first supporting frame 5. The body part 8 of the laser
processing device to be described afterwards is supported by this
first supporting frame 5 and a second supporting frame 6.
Therefore, the body part 8 of the laser processing device to be
described afterwards is floatingly supported to be movable in the
up and down directions.
The body part 8 of the laser processing device has a laser
irradiating section 10 into which an optical fiber 9 is inserted
and a head section 11, and the head section 11 comprises a
cylindrical body section 12 and a nozzle section 13.
The cylindrical body section 12 consists of a cylinder body 14
which is open at the top and the bottom as shown in FIG. 4, and the
cylinder body 14 has, inserted into it, a cylinder portion 15
having a condenser lens 16 for condensing a laser beam sent from an
oscillator (not shown) via the optical fiber 9 and a protective
glass 17 for protecting the condenser lens 16 from floating matters
generated by welding, both built into the cylinder portion 15.
An annular slit 18, consisting of an annular space, is formed
between the cylinder body 14 and the cylinder portion 15. That is,
the annular slit 18 is so formed as to surround the exterior of the
condenser lens 16 and the protective glass 17. Further, the upper
part of the annular slit 18 is blocked, and its lower part is open
to communicate with the inside of the nozzle section 13 by way of
an annular opening 18a. A secondary air inlet 19 communicates with
the annular slit 18. These annular slit 18, the nozzle section 13,
the secondary air inlet 19 and the like constitute secondary air
delivery means.
Therefore, when secondary air (pressurized air or inert gas) A2 is
fed in through the secondary air inlet 19, that secondary air A2
fully permeates the annular slit 18, and then jets out as a
cylindrically shaped air curtain from the annular opening 18a in
the lower part into a conic section 20 of the nozzle section
13.
The nozzle section 13 is formed of the tapered conic section 20
whose bore shrinks from top toward bottom, and the upper and lower
ends of its internal space 21 are open. The upper end of the
internal space 21 is formed to have a bore communicating with the
annular opening 18a of the annular slit 18. Further, the inner face
of the conic section 20 is formed in a taper shape whose diameter
shrinks toward the bottom along the external shape of a laser beam
L from the condenser lens 16.
The conic section 20 of the nozzle section 13 is so provided as to
be linked to or separated from the cylinder body 14 of the
cylindrical body section 12 by turning a bolt or a screw clockwise
or counterclockwise, and separating it facilitates maintenance of
the condenser lens 16 and the protective glass 17.
On a part of the lower end of the conic section 20 in the nozzle
section 13, namely on the reverse side to the progressing direction
of welding (the progressing direction of processing) X, a support
piece 22 formed by extending the conic section 20 downward is
provided as shown in FIG. 6, and underneath the conic section 20
there is provided a space section 23, open on the side of the
progressing direction of welding X and on both sides in the
direction orthogonal to that direction.
A bracket 24 is fastened to the support piece 22 in a direction
reverse to the progressing direction of welding X and on a side of
the support piece 22 as shown in FIG. 4, and the bracket 24 extends
downward from the support piece 22. In the bracket 24, a long hole
25 is formed which opens in the direction orthogonal to the
progressing direction of welding X and is long in the up and down
directions. On the side of the bracket 24 where the laser beam L
passes, a holding member 26 is arranged in such a position that the
holding member does not obstruct the passage of the laser beam L.
The holding member 26 is provided by a screw 27 inserted into the
long hole 25.
A side nozzle 28 constituting gas delivery means is inserted into
and fastened to the holding member 26, with a jetting outlet at its
lower end oriented in the progressing direction of welding X and
toward the vicinity of the focal point F of the laser beam L. By
loosening the screw 27, the side nozzle 28 can be turned together
with the holding member 26 around the screw 27 to control the
variation of its angle (posture) toward the welding face WL, and by
tightening the screw 27, the controlled position (posture) can be
held. In FIG. 4, an angle .alpha. between the side nozzle 28
indicated by a solid line and the side nozzle 28 indicated by a
chain line represents the controllable range; in both cases, the
jetting outlet at the lower end of the side nozzle 28 can be
oriented toward the vicinity of the focal point F of the laser
beam.
A shield gas inlet 29 is connected to the upper end of the side
nozzle 28, and shield gas G let in through the shield gas inlet 29
is jetted from a jetting outlet at the lower end through the side
nozzle 28 to the vicinity of the focal point F. Thus, the shield
gas is present all the time in the vicinity of the focal point F
and constitutes an atmosphere to shield the weld.
A covering member 30 is fastened, positioned on the inner face of
the bracket 24 in the progressing direction of welding X and on an
upper side of the side nozzle 28. The covering member 30 is formed
in a box shape lacking a wall only on the progressing direction of
welding X, as shown in FIG. 6, and has a full opening 30a on a side
in the progressing direction of welding X. Further, as shown in
FIG. 6, a laser beam passing hole 30c is bored into the upper wall
30b of the covering member 30, and another laser beam passing hole
30e is bored into the lower wall 30d. Further, on the rear wall 30f
reverse to the progressing direction of welding X, two
substantially horizontal slit-shaped outlets 31, penetrating the
wall in the back and forth directions, are formed in upper and
lower positions.
Further, a chamber 32 is disposed behind the rear wall 30f of the
covering member 30, and the chamber 32 and the slit-shaped jetting
outlets 31 communicate with each other. Further, a primary air
inlet 33 is connected to the chamber 32. Primary air A1 that is
supplied is jetted out from the two slit-shaped jetting outlets 31
through the chamber 32, circulates in a substantially horizontal
air curtain form within the covering member 30, and is jetted out
in the progressing direction of welding X from the opening 30a.
Incidentally, the primary air curtain of primary air A1 jetted out
of the covering member 30 and the slit-shaped jetting outlets 31
need not be horizontal relative to the progressing direction of
welding X in every case, but can be inclined upward or downward as
required. However, if it is excessively inclined, the air curtain
may roll in and diffuse shield gas G, and therefore its
inclination, if any, should be kept within the extent of not
rolling in shield gas G.
Primary air delivery means is configured of the slit-shaped jetting
outlets 31 and other elements.
On a side of the cylindrical body section 12, a supporting arm 34
is firmly fitted as shown in FIG. 1 and FIG. 5, and the supporting
arm 34 hangs down as far as to a position underneath the covering
member 30.
A following roller 35 and wiper members 36 are attached to the
lower end of the supporting arm 34. The following roller 35 is
attached with an allowance for idling to a rotation shaft 37
provided on the supporting arm 34 in a horizontal direction
orthogonal to the progressing direction of welding X. Further, the
following roller 35 is formed of a disk and arranged in a space
between the covering member 30 and the focal point F of the laser
beam, and has a diameter as large as possible to serve as a side
wall in the space between the focal point F and the covering member
30 for preventing diffusion of floating matters.
It is desirable for the position of the following roller 35 in the
direction orthogonal to the progressing direction of welding X (the
position in FIG. 5) to be disposed such that the following position
of the following roller 35 (the position in which it is contact
with the work) is as close as practicable to the focal position of
the laser beam, and for the position of the following roller 35 in
the progressing direction of welding X (the position in the right
and left direction in FIG. 4) to be disposed such that the
following position (the position of contact with the work) B of
that following roller 35 is the same as the focal point F of the
laser beam. The position in the height direction is not always the
same, varying with the focal depth of the laser beam relative to
the work and other factors.
Two wiper members 36 are disposed in a substantial V shape, fixed
to the lower end of the supporting arm 34. These wiper members 36
are arranged in parallel with slight gaps from a face of the
following roller 35 on a side of welding, and immediately scrape
off sputters sticking to the face of the following roller 35 on the
side of welding in collaboration with the rotation of the following
roller 35. The number and shape of these wiper members 36 can be
selected as desired.
The shield gas (assist gas) may consist of argon, helium gas,
nitrogen gas or a mixture of any of them as appropriate.
As the primary air A1 and secondary air A2, the shield gas may as
well be used.
Further, the laser oscillator may be either a CO.sub.2 laser or a
YAG laser, and the laser welding may be so-called hybrid welding
combining laser welding with arc welding, or may involve combined
use of a welding wire in combination with these techniques.
Next, the actions that take place in welding will be described.
First, before the start of welding, the fitting frame 1 is brought
down with an actuator 70 shown in FIG. 7 and, after the following
roller 35 comes into contact with the work, is brought farther down
to a position where the elastic member 4 shrinks by a certain
quantity (e.g. 5 to 10 mm). This makes possible floating support
during the welding while restraining with the pressing force of the
elastic member 4 the up and down movements of the body part 8
ensuing from the up and down movements of the following roller
35.
When the fitting frame 1 of the laser processing device moves in
the progressing direction of welding X relative to the work, the
body part 8 supported by the fitting frame 1 also moves in the
progressing direction of welding X.
This movement subjects the lower end of the following roller 35 to
a force in the up and down directions following the upper face
(welded face WL) of the work. This force is transmitted to the head
section 11 via the supporting arm 34 and the body of the cylinder
14, and causes the supporting frames 5 and 6 floatingly supported
by the fitting frame 1 to move up and down. Thus, the following
roller 35 and the whole body part 8 move up and down to the same
extent. Therefore, the condenser lens 16 built into the body of the
cylinder 14, follows the up and down movements of the following
roller 35, and moves up and down to the same extent, and the focal
point F of the laser beam is always on the prescribed position of
the work irrespective of the shape of the work.
Then, laser welding is accomplished by irradiating the weld of the
work with the laser beam.
Next, the conditions of the shield gas and the air curtain in the
welding state will be described with reference to FIG. 6.
During the welding process, the shield gas G supplied from the
shield gas inlet 29 is jetted out as indicated by an arrow H onto
the vicinity of the focal point F of the laser beam via the side
nozzle 28, and performs the role of keeping the welding process
stable.
The primary air A1 supplied from the primary air inlet 33 flows
into a chamber 32, then horizontally jets out into the covering
member 30 from the two slit-shaped jetting outlets 31 formed in the
covering member 30, and continues to jet out in the progressing
direction of welding X, forming two upper and lower layers within
the covering member 30 as indicated by arrows I and expanding
laterally in each layer. These jet flows of the primary air A1
prevents floating matters generated from the vicinity of the focal
point F of the laser beam L (welded portion) from being blown
up.
However, such a primary air curtain alone, formed of the primary
air A1 in the horizontal direction, is not enough; part of the
floating matters may avert the primary air curtain or be blown up,
rolled in by the counter flows of the primary air curtain to reach
the space section 23 above the covering member 30, and the floating
matters may stick to the protective glass 17.
In view of this problem, according to the invention, a secondary
air curtain consisting of the secondary air A2 is generated as a
further precaution.
Thus, when the secondary air A2 is supplied from the secondary air
inlet 19, that secondary air A2 is introduced into the annular slit
18 in the body of the cylinder 14 and jetted out downward from the
annular opening 18a of that annular slit 18. This jetted secondary
air A2 hangs down as an air curtain in a tapered cylindrical shape
covering (shielding) the luminous flux of the laser beam L from the
outside, as indicated by arrow J in FIG. 6, and reaches the space
section 23 above the covering member 30.
In such a state in which the secondary air A2 is flowing down in a
cylindrical air curtain shape, even if there are floating matters
rolled up beyond the covering member 30, the flow of the secondary
air curtain of the secondary air A2 will prevent the floating
matters from invading into the air curtain, which will have a
shielding effect. Therefore, floating matters cannot reach the
protective glass 17.
Having completed this role to prevent floating matters from being
blown up, the air curtain having reached the vicinity of the area
above the covering member 30 disappears, and that secondary air A2
is rolled in by the power air curtain flow of the primary air A1
and forcibly turned and rejected toward the progressing direction
of welding X, thereby to prevent the secondary air A2 from staying
above the covering member 30.
Thus, if the secondary air A2 stayed above the covering member 30,
its momentum as the secondary air curtain formed of secondary air
would be weakened to make the shielding effect be lost, and the
succeeding secondary air curtain would not be formed in a
satisfactory way, but the prompt rejection of the secondary air A2
in the progressing direction of welding X as described above
eliminates this problem.
Furthermore, as stated above, the secondary air joining with the
primary air curtain and flowing in the same direction (the
progressing direction of welding X) results in substantial
expansion of the primary air curtain of the primary air A1, which
strengthens the effect of preventing floating matters from being
rolled into the area above the covering member 30 from the lower
part of the primary air curtain.
Therefore, according to the invention, not only the individual
shielding effects by the relative air curtains of the primary air
A1 and of the secondary air A2 but also the mutually reinforcing
effect of the primary air A1 and the secondary air A2 can be
expected, and this mutually reinforcing effect can almost
completely prevent floating matters from sticking to the protective
glass 17.
Incidentally, it is desirable for the flow rate of the primary air
A1 to be greater than the flow rate of the secondary air A2, and a
satisfactory result was obtained when the flow rate ratio between
the primary air A1 and the secondary air A2 was about 4:1, though
the optimal ratio may differ with given conditions.
Further, as the laser beam passing hole 30c is bored into the upper
part of the covering member 30, part of the secondary air A2 flows
into the covering member 30 from this laser beam passing hole 30c,
and the secondary air A2 joins with the primary air curtain to flow
in the progressing direction of welding X. Therefore, the secondary
air flowing downward through the laser beam passing hole 30c
counters the flow of floating matters otherwise blown up through
the upper and lower laser beam passing holes 30c and 30e of the
covering member 30, resulting in an enhanced shielding effect
against the floating matters.
Thanks to these actions, the use of this embodiment of the
invention has provided a result that the required cleaning
frequency of the protective glass, which was previously once every
hour, has been reduced once a day, namely no more than the usual
frequency of routine daily inspection.
After the completion of the laser welding described above, the
fitting frame 1 is raised and returned to its original position
with an actuator (not shown).
Although the configuration of the following device in this
embodiment is such that the following roller 35 is brought into
contact with the work and the head section 11 and other elements
are raised or lowered, the following device may as well be a
non-contact type comprising a displacement sensor which detects the
gap between the tip of the head section and the work without making
contact and control means which keeps the gap constant in response
to the value detected by this displacement sensor, as described in
JP-B2-2514138.
This embodiment in which the axis of the cylindrical secondary air
curtain of the secondary air A2 hangs down past the center of the
laser beam passing hole 30c on the upper face of the horizontal
covering member 30 to make the secondary air A2 coaxial with the
laser beam L is the most suitable, but the secondary air A2 may as
well be jetted out in the following manner.
Although it is desirable for the air curtain of the secondary air
A2 to be coaxial with the laser beam L as in the embodiment
described above, if coaxial arrangement is impossible structurally
or for any other reason, the secondary air A2 may be jetted
downward in a state of surrounding the condenser lens 16 and the
protective glass 17 insofar as practicable, or jetted downward from
the vicinity of the condenser lens 16 and the protective glass 17
or jetted out farther downward from these two elements. In one of
these ways, the similar actions and effects to the foregoing can be
achieved.
Or, where it is impossible structurally or for any other reason to
have the secondary air A2 descend vertically downward, it may have
some angle, but the angle should be set within a range in which the
secondary curtain of the secondary air A2 and the primary air
curtain of the primary air A1 can smoothly join each other. In this
way, the similar actions and effects to the foregoing can be
achieved.
The progressing direction of welding X means not only the direction
in which this laser processing device is progressing (moving) when
the work is at halt, but also includes the direction in which
welding progresses when this laser processing device is at halt and
the work is moving in the direction relatively reverse to that of
the laser processing device, and further the direction in which
welding progresses when both the laser processing device and the
work are moving in the directions relatively reverse to each other.
Thus, it means the progressing direction of welding in the relative
moving directions of the laser processing device and of the
work.
Therefore, the invention can also be applied to a case in which
arcuate portions are welded as the focal position of this laser
processing device moves in the progressing direction of welding
while matching the arcuate portions to be welded wherein the
cylindrical work is turned while the laser processing device is
kept fixed. An embodiment in this case will be described with
reference to FIG. 7 and FIG. 8.
The work to be used in this embodiment is a work W, which is formed
in an advance process as a vessel by firmly fitting together, with
no fitting gap, one metallic structure W1 formed in a bowl shape
and another metallic structure W2 formed also in a bowl shape.
First, the work W placed in a position not shown is held with a
clamp section 51 provided at the tip of a robot arm 50 and carried
to the laser processing device.
This clamp section 51 is coupled with a tool holding shaft 52
rotatably equipped on a rotation axis 50a provided at the tip of
the robot arm 50 and, by being turned by rotation driving means
built into the robot arm 50 itself, the tool holding shaft 52 turns
in one direction (the direction indicated by arrow K) to turn the
clamp section 51 in the circumferential direction, and that turning
position is fixed by a random indexing device 53.
In the embodiment shown in FIG. 7, the work W is a muffler for
automotive use and, as shown in FIG. 8, an inlet pipe and an outlet
pipe 54 protrude by a few mm from both end faces of that muffler.
Thus, this protruding section 54a is utilized as the member for
positioning the indexing direction.
Further, the clamp section 51 has a stopper 55 which hits against
one end face of the work W and a pair of clamps 56 for holding or
releasing the work W. The opening and closing of the clamps 56 are
driven by an air cylinder (not shown) built into the clamp section
51.
On the side opposite to the clamp section 51, a rotation receiving
section 57 is arranged, and the rotation receiving section 57 is
provided with a disk 59 which, rotatably disposed, rotates around a
rotation axis 58 which is coaxial with the tool holding shaft 52 of
the robot arm 50. Further, the rotation receiving section 57 is
moved forward and backward along the rotation axis 58 by an
actuator (air cylinder) 60, and the forward movement (movement
toward the rotation axis 50a) of the rotation receiving section 57
causes the disk 59 to hit against the other end face of the set
work W to clamp the work W while the backward movement causes the
disk 59 to move away from the work W to release the work W from the
clamping.
On the rotation receiving section 57 side, a stopper 61 which is
moved upward and downward by an actuator (not shown) is provided,
and the descent of the stopper 61 restricts the rotation of the
disk 59, while the ascent of the stopper 61 enables the disk 59 to
rotate.
Next, the operation of the embodiment shown in FIG. 7 will be
described.
The work W clamped by the clamp section 51 of the robot arm 50 is
carried to the laser welding section, keeps the axis of that work W
in a horizontal state, and sets one end face of that work W in the
M position shown in FIG. 7. After this positioning is done, the
disk 59 is moved by the actuator 60 leftward in the drawing and
hits against the other end of the work W in the P position in FIG.
7 to absorb any fluctuation of the work W in the axial direction.
This causes the welding position, which is the fitting section 62
in the work W, to be correctly set in the position of the focal
point F of the laser beam in the body part 8 of the laser
processing device. Incidentally, after the work W is positioned in
the direction of the rotation axis 50a as described above, it is
preferable for the clamps 56 to be closed after being opened once
to eliminate any deviation of the axis of the work W from the
rotation axis 58.
After the work W is positioned as described above, the process
progresses to the laser welding step.
After the work W is positioned, the head section 11 of the laser
processing device is brought down by the elevating actuator 70 to
its prescribed position and fixed there. At this time, the
following device including the following roller 35 mentioned above
positions the focal point F of the laser beam on the weld.
The stopper 61 of the rotation receiving section 57 is raised by an
actuator (not shown) to release the rotation of the disk 59 from
the restriction.
At the same time as the emission of the laser beam L, the work W is
rotationally driven by the clamps 56 in the direction K, and the
whole circumference of the fitting section 62 of the work W is
laser-welded by the laser beam. Then the disk 59 is rotated by
following the rotational force of the work W.
In the laser welding as in the above-described case, the shield gas
G, the primary air A1 and the secondary air A2 are supplied to
carry out welding, with air curtains similar to the foregoing being
generated.
When the welding is completed as the work W has rotated 360 degrees
plus the equivalent of welding lap, the head section 11 ascends and
returns to its original position.
After that, the work W is moved leftward in FIG. 7 together with
the clamps 56 by the robot arm 50, and the work W is released from
the laser welding section to be carried to the next step.
After the release of the work W, the disk 59 of the rotation
receiving section 57 is rotationally returned to the original
indexing position by a weight (not shown), and the stopper 61
restricts the rotation of the disk 59.
Incidentally, in non-planar welding, since it is preferable from
the viewpoint of welding posture for the weld to be always on the
top face, it is desirable for the laser beam to hang down
vertically and for the work W to be moved in welding a circular
circumference as in this embodiment.
Further, since the rotation receiving sections 57, such as the ones
described above, are usually arranged opposite each other on two
sides, the work is brought in between them with a robot arm, that
work is pinched by the two rotation receiving sections and the work
is turned by the driving of those rotation receiving sections 57,
each work is pinched and released by the robot arm twice each.
Unlike this, in this embodiment not only can one of the rotation
receiving sections 57 be dispensed with by providing the wrist of
the robot arm with a function to clamp the work and a function to
turn the work, but only each work can be pinched and released by
the robot arm only once each, resulting in a substantial saving in
the time taken to set and release the work, which means a
significant advantage in a mass production process.
Another embodiment different from the foregoing will be described
next.
Where the aforementioned following roller 35 is used in the
foregoing embodiment, the accuracy of welding can be further
enhanced by monitoring the frequency of revolutions, angular
velocity and other factors of the following roller 35 in its idling
state and utilizing the information thereby obtained for verifying
the welding speed.
In welding the outer circumference of a work having a non-circular
section while turning it around its axis, the welding speed of the
outer circumference fluctuates even if the angular velocity of
turning is constant. For this reason, even if the welding speed of
the outer circumference is programmed and the angular velocity is
variably set, monitoring the frequency of revolutions, angular
velocity and other factors and utilizing the information thereby
obtained for verifying the welding speed would make it possible to
verify the actual welding speed on a real time basis, correct the
angular velocity on that basis and thereby enhance the accuracy of
welding.
More specifically, either the axial rotation of the following
roller 35 may be directly detected with a rotation sensor (encoder
or the like) or the following roller 35 may be indirectly measured
with optical means (a photodiode, CCD or the like).
Such an embodiment can serve to further enhance the quality of
welding.
Incidentally, while this embodiment represents an application of
the invention to a welding device, applications of the invention
are not limited to welding, but cover an extensive range of devices
including those for laser processing, such as cutting or marking
with a laser beam.
Therefore, in the foregoing cases of carrying out welding, the X
direction is supposed to be the progressing direction of welding,
but as the invention covers the aforementioned modes of processing
other than welding, this X direction is the progressing direction
of processing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an embodiment according to the present invention as
seen in the progressing direction of processing.
FIG. 2 shows a right side profile of FIG. 1.
FIG. 3 shows a plan of the view of FIG. 1.
FIG. 4 shows a partially exploded view of the essential part in
FIG. 1.
FIG. 5 shows a view as seen from the right side in FIG. 4.
FIG. 6 shows a sectional view of the flows of air in FIG. 4.
FIG. 7 shows an example of application of the invention to the
welding and production of a vessel.
FIG. 8 illustrates the positioning of the direction of indexing the
work in FIG. 7.
* * * * *